Guitar into amp and captor into audio interface is about the same as guitar into amp and return to helix, a bit less noise.

So the Send is adding in most of the hum and a lot of high frequency noise.

I just tried an Ebtech Hum Eliminator in the send from the helix to the amp and it gets much better, basically knocks out the > 100hz hum and reduces 50hz by 6db and 100hz by 9db and also around 9db reduction in high frequency noise.

I will try it without the Furman, might be a bit difficult to get everything off of it so I will test with headphones with just the Helix and the Amp...